Seating depth issue 40 S&W

[recon14]

Ok so I loaded up some of the new 180 TCFP I recieved from Falcon yesterday. Started with 4.9 of 231 and seated them to 1.125. They failed ty the "plunk" test and would not fully seat in the chamber in my sigma.

I had to go down to 1.114 to get them to seat fully in the chamber. What will that do to my pressures? They are .628 in length and .401 diameter. My standard 180 are .638 in length so I am hoping all should be fine.

Can anyone please help with a pressure calc or insight? Thanks

 

[Tom Beavert]

Plunk?

Sorry, I can't help with pressure - been loading 180 gn, X-Treme over your load of 231. The copper plated lead mic at 0.572 and at 1.125 plunk fine in my M&P 40 bbl, and shoot great.
Someone will jump in with pressure facts.
good luck
tb

 

[Rule3]

They failed the plunk test, but did you crimp them? What is your crimp dimension?

 

[BLUEDOT37]

One load manuals list OAL for a Hornady 180gr at 1.125" & 5.0grs max. Another shows OAL for a Sierra at 1.115" @ 5.6grs max. Of course the bullet shape helps define the OAL. If Falcon doesn't provide any OAL numbers for this bullet you could just play it safe & drop your charge a few tenths & test fire a few to see where you're at, & adjust accordingly.

 

[Titegroups]

The .011 aint going to hurt you but the failed plunk test says you got sometjinh else going on you need to resolve before going fruther.

 

[recon14]

It failed the plunk test because I originally a seated the bullet to my usual length which was too long for this particular bullets shape. As soon as I seated it deeper it fit fine. I was just wondering what seating it deeper then normal would do to the pressure.

sent from my S III using TapaTalk

 

[Rule3]

It failed the plunk test because I originally a seated the bullet to my usual length which was too long for this particular bullets shape. As soon as I seated it deeper it fit fine. I was just wondering what seating it deeper then normal would do to the pressure.

sent from my S III using TapaTalk

I understand what you did but if the case is not taper crimped it may fail the "plunk" test.

The case seats on the case mouth and if it is too wide it will not camber, It may hit the case mouth and not actually be hitting the bullet.

What is the diameter at the case mouth with the bullet seated (crimp value)?

Yes seating a bullet deeper can increase the pressure but I can not say as I have not used your bullet. Where did you get the 1.125 OAL from? Not all bullets are the same so that length means nothing if it was not the bullet you are using.

Bottom line seat and crimp the bullet then keep trying the barrel test until it chambers. Start at the low end of the powder you are using.

Why won't my reloads chamber? A short throat is sometimes the culprit. Too long an O.A.L. is sometimes the problem, even with barrels with average throats.

This pic is often used to help explain correct headspacing and how O.A.L. can affect chambering and headspace.

 

[Titegroups]

Reduced case volume means higher pressures. You should aleeady know this. On short high pressure cases like 9mm and 40 this becomes more critical due to the fact a small (.010) difference for example is a greater percentage of the case volume than on a long revolver case ie. 357, 44, 45colt. I have no way testing this buy I would guess a few thousand psi.

 

[recon14]

Thanks to everyone for the info and what to look for.

They are taper crimped the same as my other 40 loads. The only reason they didn't initially seat was the OAL from the slightly different bullet shape.

I have a few ready to go and will test fire them looking for overpressure signs.

I am also going to do a few rounds with a slightly lower charge and fire them first looking for pressure warning signs as well. I also have a message into Falcon asking if they have any recommended recipes.

sent from my S III using TapaTalk

 

[Trini]

The factory rounds that I check are OAL is 1.135. Loading shorter will in pressure. It doesn't take much to increase the pressure to dangerous levels. What factory ammo have you shot thru your Sigma? What is the OAL? Did it pass your chamber test? A taper crimp is the way to go. Good luck...

 

[mtgianni]

Before firing them I would reduce my load 5% and fire several. Then I would fire some reduced 2.5%. If these show no adverse pressure signs I would fire my standard load.